ERBB2 and neoplasm: Furthermore, in in vitro studies, splenocytes of naive and T-DXd–treated mice were cocultured with both HER2-expressing and non-HER2-expressing tumor cells, and the splenocytes of T-Dxd–treated mice reacted to both tumor cells with increased IFN-γ secretion, whereas the splenocytes of naive mice did not (76).